Abstract: Although substantial progress was made in reducing alcohol-impaired driving fatal crashes between 1982 and 1997, the numbers have stalled over the last decade, and approximately 13,000 people are killed each year in these crashes. Although increased, improved and/or more efficient law enforcement holds the most promise for further reducing impaired driving, enforcement of drinking-and-driving laws is never without cost, and it must compete against other law enforcement activities, especially given the current economic strain on local and State budgets. How much of a reduction in drinking and driving would be achieved by how much improvement in impaired-driving law enforcement? How does the relationship between marginal increases in enforcement intensity and reductions in impaired driving differ across enforcement approaches? Decision-makers, public officials, and community organizations facing such policy and budgetary dilemmas would benefit from a better understanding of the association between improvements in the enforcement of drinking-and-driving laws and reductions in impaired driving. With city, county, and state budgets constricted by the current recession and police department workloads being increased with the requirements for national security operations, it is particularly important to implement DUI enforcement methods that are highly efficient. Certainly a goal in any community is to reduce the deaths, injuries, and property damage due to alcohol-impaired driving crashes. This study proposes to take advantage of driver BAC and self-report data on drinking and driving from the 2007 National Roadside Survey (NRS) and augment these data with information collected from police departments operating in the 60 NRS sites regarding the types and levels of DUI enforcement activities conducted in 2007 and reported traffic crashes in that jurisdiction. This unique data set will allow the first such exploratory assessment of the relationship of enforcement intensity (with measures from both traditional DUI enforcement and sobriety checkpoints) to the prevalence of drinking and driving on the roads. Then both of these measures will be related to alcohol-related crashes. This exploratory study is novel in that it will measure the objective of enforcement programs, which is deterrence, more directly through the more proximal mediating variable of impaired driving (as measured through BAC data of drivers on the roads) compared to previous evaluations that have typically only measured the more distal outcome-crashes. Although crashes are an important outcome, they are one step further removed from enforcement by the many non-enforcement factors that determine crash frequency. Understanding how police activities affect the prevalence of impaired driving may help explain differential outcomes on crashes that have been associated with the enforcement procedures being examined. PUBLIC HEALTH RELEVANCE: Public Health Relevance: In 2007, an estimated 12,998 (32%) of the 41,059 traffic fatalities involved an impaired driver (i.e., the driver's BAC was e.08 g/dL). An additional 512,000 people are injured in alcohol-related crashes each year, and alcohol- related crashes cost the U.S. society $51 billion annually. This study promises to provide new insights into the effectiveness of DUI enforcement through traditional police patrols and sobriety checkpoints by relating current enforcement activity levels in both areas to the prevalence of impaired drivers on the road and to alcohol-related crashes.